I haven't found a best time of day. If the sun is out, it causes trouble. There are paths in the chasm, and you can tube down part of it... for an entrance fee: www.AusableChasm.com
My brother lives just a short walk down Chasm Road.
Whiteface Mountain (in Lake Placid) is about 40 minutes away, and worth a half-day trip. You can drive most of the way up, then walk up the spine in this photo. I took my daughters up when they were six & nine years old. It was a little scary for them, but they're battle-hardened by my parenting.
I always stay at my brother's place, so have never looked into rental places. In recent news in the area, there has been some flooding along the shores of Lake Champlain, swamping cottages, which may affect rentals this summer. The above website has some resources.
Looking across Lake Champlain from near Keeseville, toward Vermont can offer many nice, golden sunrises.
Keeseville also has some good views along the river in town.